The conversion of oxygenated hydrocarbons to oxygen free hydrocarbons by reacting the oxygenated molecules in the presence of an acid catalyst is well known. More recently, it has been shown that certain classes of such oxygenated molecules may be converted rather easily to hydrocarbon products over acidic solid surfaces such as those present in crystalline aluminosilicate zeolites with high silica to alumina ratios. Those molecules which convert easily include monofunctional aliphatic alcohols, ethers, aldehydes, and analogs thereof. Zeolites effective in this conversion include mordenite, offretite, and certain synthetic zeolites such as those described in U.S. Pat. Nos. 3,894,107 or 3,899,544. Generally, these conversions are effective only for molecules with 8 carbons or less. Larger molecules may be converted, according to the literature (Science 206, Oct. 5, 1979) if a hydrogen atmosphere is present and if the carbon to oxygen ratio in the molecule is reasonably high, e.g., more than 8-10.
Other classes of oxygenated molecules exist which are more difficult to convert to oxygen-free hydrocarbons. These include short chain acetates, carboxylic acids, carbohydrates, cellulose, and other highly oxygenated polymeric species. U.S. Pat. No. 3,998,898 to Chang, et al, teaches that these molecules may be converted to hydrocarbons if (1) they have 8 carbons or less, and (2) they are reacted in the presence of a substantial quantity of "easily convertible" molecules such as short chain alcohols. In this patent, a relation R is defined wherein R&gt;1 for any oxygenated molecule which is easily convertible to hydrocarbons and R&lt;1 for any oxygenated molecule which is difficult to convert to hydrocarbons. This patent teaches that the overall mixture of hydrocarbons to be converted must have a cumulative R value &gt;1 for successful conversion to hydrocarbons even though that mixture may contain some oxygenated molecules with R&lt;1.
As disclosed in U.S. Pat. No. 3,998,898, R is calculated from the formula R=m-2p/n wherein m is the number of hydrogen atoms in the molecule, p is the number of oxygen atoms in the molecule, and n is the number of carbon atoms in the molecule.
The preferred catalyst for the above discussed conversion is a synthetic, shape selective zeolite whose properties are discussed therein and which is admixed with high surface area alumina binder. As will be shown below, the presence of the alumina binder contributes significantly to coke formation during the processing of oxygenated molecules which are difficult to convert to hydrocarbons, i.e., R&lt;1. In addition, it will be shown that in accordance with the instant invention oxygenated hydrocarbons of any carbon to oxygen ratio, R value, or carbon chain length can be converted to oxygen-free hydrocarbons through a unique combination of a crystalline, aluminosilicate zeolite and a proper diluent for such zeolite.